Drive unit, particularly rear drive unit, for an all-wheel drive of a motor vehicle

ABSTRACT

A drive unit, such as a rear drive unit, for a motor vehicle, such as an all-wheel drive motor vehicle, includes, but is not limited to two drive shafts, of which one drive shaft serves for driving the one wheel and the other drive shaft serves for driving the other wheel of a motor vehicle. Also provided is a transmission operationally connected to the drive shafts, through which a drive torque acting on the input of the transmission can be divided or is divided into at least two output torques and through which the output torque of the transmission acting on the one drive shaft is reversible or is reversed in its operation direction relative to the output torque of the transmission acting on the other drive shaft.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 102010 053 414.5-26, filed Dec. 6, 2010, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The technical field relates to a drive unit, particularly rear driveunit, for an all-wheel drive of a motor vehicle. The technical fieldfurthermore relates to a motor vehicle with such a drive unit, and alsorelates to an all-wheel drive.

BACKGROUND

An all-wheel drive in a motor vehicle serves for the improvement of thetraction, in order for example to make possible or at least favor acertain off-road capability of the vehicle. By driving all wheels incontact with the ground, the slip of each individual wheel is minimized.An all-wheel drive is therefore frequently installed in vehicles thatwere designed for a use in difficult terrain or on unpaved roads. Inaddition to off-road vehicles, the all-wheel drive is increasinglyemployed also in pure road vehicles. Because of the increased traction,the all-wheel drive then offers the possibility of optimallytransmitting the motor outputs that are on the increase today and thusimprove the driving stability of the vehicle. However, the componentsthat are additionally installed in a vehicle with all-wheel drive resultin that the vehicle with all-wheel drive has a higher vehicle weightcompared with a vehicle without all-wheel drive, resulting in a certainadditional consumption of fuel.

During the course of new developments, the aim therefore is an all-wheeldrive that has a reduced additional consumption of fuel. In addition,the aim also is a further improvement of the driving dynamics ofvehicles with all-wheel drive. At least one object is to provide a driveunit, particularly rear drive unit, particularly for an all-wheel driveof a motor vehicle with the features mentioned at the outset, throughwhich a vehicle with low additional consumption of fuel and an improveddynamic behavior can be realized. In addition, other aims, objects,desirable features, and characteristics will become apparent from thesubsequent summary and detailed description, and the appended claims,taken in conjunction with the accompanying drawings and this background.

SUMMARY

A drive unit, particularly rear drive unit, particularly for anall-wheel drive of a motor vehicle is provided that comprises two driveshafts, of which one drive shaft serves for driving the one wheel andthe other drive shaft for driving the other wheel of a motor vehicle,particularly of a common axle unit or axle assembly of a motor vehicle,such as for example the front axle or rear axle. To this end, one of thedrive shafts can be preferably connected to the one wheel and the otherdrive shaft to the other wheel in a rotationally fixed manner. The driveunit can be installed for example in an all-wheel drive of anautomobile, particularly passenger car or commercial vehicle. Here, theall-wheel drive is preferably of a mechanical type.

The drive unit comprises a transmission that can be operationallyconnected or is operationally connected to the drive shafts, throughwhich transmission a drive torque acting on the input of thetransmission can be divided or is divided into at least two drivetorques and through which the drive torque of the transmission acting onthe one drive shaft can be reversed or is reversed in its operationaldirection compared with the drive torque of the transmission acting onthe other drive shaft. This measure produces an improved dynamic drivingbehavior of a motor vehicle, since through the output torques actingopposite in their operation direction the yaw angle of the vehicle isinfluenced. On the one wheel or the one drive shaft a drive torque acts,which is opposed to the drive torque on the other drive shaft, asteering action having a specifically supporting effect is generated.Because of this, the dynamic driving behavior of a vehicle, particularlyin rapidly negotiated curves, is improved and thus the risk reduced,that the driver himself loses the control over the vehicle in such anextreme situation.

By dividing or branching the drive torque into the at least two outputtorques the motor for generating the drive torque can be dimensionedwith lower output than with a drive of the drive shafts by a motorassigned in each case. It has furthermore been shown that the tractionof the vehicle, particularly at low driving speed, is substantiallyimproved.

The output torques acting on the drive shafts in opposite directions toeach other have an over-steering or under-steering effect particularlywhen the motor vehicle negotiates a curve, depending on whether anoutput torque is applied to the wheel on the inside of the curve or tothe wheel on the outside of the curve, which output torque acts oppositeto the driving movement of the motor vehicle.

Through the drive unit, it is thus possible, because of the drivetorques acting in opposite directions, to influence the driving behaviorof the motor vehicle in such a manner that the motor vehicle no longerover-steers or under-steers when negotiating a curve. Preferably, theleft wheel and the right wheel of a common axle assembly of the motorvehicle are driven by the drive unit according to the invention.Preferably, the drive unit is employed as rear drive unit. The left rearwheel and the right rear wheel are driven by the drive unit. It isobviously likewise conceivable that the drive unit is a front driveunit, through which the left front wheel and the right front wheel aredriven.

It is appropriate that the transmission is designed to divide the drivetorque into two-output torques of the same size or substantially thesame value. Such a transmission with two-output torques of the sameamount can be realized in manufacturing terms with relatively littleexpenditure, since same transmissions can be utilized in order to dividethe drive torque equally over the output torques. Preferably, thetransmission is of a mechanical type. It is also conceivable that thetransmission is of an electric or electronic type.

A shifting device is provided, through which the force flow of the driveunit to the input of the transmission can be interrupted. By decouplingthe transmission from the force flow of the drive unit the motor of thedrive unit generating the force flow and the transmission modules andother mechanical components connected downstream of the motor ifapplicable are separated from the transmission. During driving movementof a vehicle, the number of the rotating parts of the drive unit isreduced as a result, when the force flow towards the transmission isinterrupted by the shifting device. Thus, reduced forces of inertiaoppose the moving of the vehicle, so that during the rolling of thevehicle a smaller dimension of friction torques or drag torques has tobe overcome.

The shifting device is preferably of the mechanical type. The shiftingdevice can be of a non-positive connection design, for example afriction clutch. The shifting device can also be of a positiveconnection design, for example a claw clutch. A shifting device designedas clutch can be provided with or without synchronizing gear orsynchronizing stage. Such a clutch can also be designed with or withoutadditional actuator. The shifting device can be of the self-shifting orexternally shifting type.

A transmission that can be operationally connected or is operationallyconnected to the drive shafts through which a drive torque acting on theinput of the transmission can be divided or is divided into at least twooutput torques acting in the same direction, of which one output torqueacts on the one drive shaft and another output torque on the other driveshaft. Because of this, the drive torque for generating a propellingforce of the motor vehicle is utilized in order to move the motorvehicle in driving direction, particularly in forward driving directionor reverse driving direction. Because of this, the transmission duringthe course of the invention is also called traction transmission.

Preferably, the traction transmission or the transmission, through whichthe drive torque is divided into the two-output torques acting in thesame direction is designed as differential gear. Through thedifferential gear, the drive shafts thus transmit the same force ontothe wheels connected to these. The circumferential velocities of thewheels can adjust themselves freely; merely a motor of the drive unitgenerating the force flow or the rotary movement predetermines the sumof the velocities of the drive shafts or the wheels. Thus, a highdriving comfort, particularly when negotiating curves, is achieved. Thedifferential gear can be a mechanical differential gear or an electricdifferential gear, which is preferably designed as axle differential.The differential gear can furthermore be a locking differential. Alocking differential is a special differential gear that serves toreduce slip on that wheel having the lower ground adhesion in such amanner that the locking differential either stiffens the drive line ordistributes more torque to the wheel having the better ground adhesion.

It is also conceivable that two differential gears are provided, ofwhich the one differential gear is a locking differential. Here, thedifferential gear or the locking differential can be optionallyactivated or deactivated. It is furthermore conceivable that thedifferential gear additionally comprises a locking differential stagethat can be activated. In addition to the differential gear adifferential lock can also be provided, which can be activated asrequired.

A shifting device is provided, through which the force flow of the driveunit towards the input of the traction transmission can be interrupted.A separation of the traction transmission from the force flow of thedrive unit can for example be carried out if the drive unit is designedas an all-wheel drive and the traction of the vehicle is to beexclusively generated by the front wheel drive. Through the decouplingof the traction transmission from the force flow of the drive unit themotor of the drive unit generating the force flow and the transmissionmodules and other mechanical components connected downstream of themotor if applicable are separated from the traction transmission. Indriving mode of a vehicle, the number of the rotating parts of the driveunit is thus reduced, when the force flow towards the tractiontransmission is interrupted by the shifting device. Because of this,lower forces of inertia thus oppose the moving of the vehicle, so thatduring the rolling of the vehicle a smaller dimension of frictiontorques or drag torques has to be overcome.

The shifting device is preferably of a mechanical type. The shiftingdevice can be of the non-positive connection design, for example asfriction clutch. The shifting device can also be of the positiveconnection design, for example a claw clutch. A shifting device designedas clutch can be provided with or without synchronizing gear orsynchronizing stage. Such a clutch can also be designed with or withoutadditional actuator. The shifting device can be of the self-shifting orexternally shifting type.

A shifting device is provided, through which the force flow of the driveunit can be directed or is directed optionally to the input of the onetransmission or traction transmission or to the input of the othertransmission. This provides a vehicle with a particularly favorabledynamic driving behavior since by means of the shifting device theoutput torque generated on the one drive shaft compared with the outputtorque generated on the other drive shaft can act in the same directionor in opposite direction depending on requirement. Through the shiftingdevice it can thus be controlled if the traction transmission is activeand thus a propelling force for propelling the motor vehicle isgenerated, or if the other transmission is active, which through thegeneration of the output torques acting in opposite direction to eachother influences the yaw torque of the motor vehicle and thus generatesa steering effect. Through the shifting device, the drive shafts can beflexibly activated. This makes possible an optimum adaptation to acurrently travelled terrain, in that the traction transmission isactivated optionally and depending on requirement. Because of this,reduced fuel consumption is furthermore achieved.

Preferably, the shifting device is designed to interrupt the force flowonto the drive shafts in a neutral position. The shifting device is thusdesigned also for decoupling the force flow from the drive shafts. Inthe neutral position, the motor and any gear units or such likecomponents connected downstream are decoupled from the drive shaft sothat for moving a vehicle a smaller number of components are put intorotary motion. The inertia effect through rotating parts in driving modeof a vehicle is reduced because of this. Because of this, reducedfriction torques are likewise obtained, so that this measure aims at areduction of the fuel consumption.

In the neutral position, the wheels connected to the drive shafts arenot driven. In the case of an all-wheel drive, the drive of the vehiclethen takes place via the other axle. If the drive unit is a rear driveunit, the drive of the vehicle in the neutral position is affected viathe front wheels.

This shifting device, which can be shifted into three operating modes,is preferably of a mechanical type, particularly designed as clutch. Theclutch can be a friction-connected clutch, for example in the manner ofa friction clutch. The clutch can also be designed as a positivelyconnected clutch, for example in the manner of a claw clutch. Theshifting device can be designed with or without synchronizing gear. Theshifting device can also be provided with or without actuator. Theshifting device can be of the self-shifting or externally shifted type.

The transmission by means of which output torques acting in oppositedirection are generated on the drive shafts is designed as planetarygear set. By means of the planetary set, which is also called planetarygear set, the dividing of the drive torque into two-output torques withopposite operating direction can be realized in a technically simplemanner. Preferably, the planetary gear set comprises at least two sungears, at least two internal gears and at least one planet gear rollingoff or meshing with the internal circumference of the internal gears andon the outer circumference of the sun gears. For the sake of runningstability in operation of the planetary gear set, at least two,preferentially three planet gears arranged distributed over thecircumference are provided, which are located between the internal gearsand the sun gears. Preferably, the at least one planet gear, the atleast one sun gear and the at least one internal gear are substantiallyarranged coaxially with respect to the center axis of the planetary gearset.

It is appropriate that seen in axial direction, two planet gears areprovided, which are arranged located one after the other and the centeraxes are each located coaxially with respect to a common axis ofrotation. The at least one planet gear can be rotatably mounted on aplanet carrier. The at least one planet gear can also be providedwithout planet carrier, so that the at least one planet gear is locatedbetween the outer circumference of at least one of the sun gears and theinner circumference of at least one internal gear in a floating manner,particularly braced between internal gear and sun gear. Insofar as seenin axial direction, two planet gears are mounted in a self-rotatingmanner about a common axis of rotation of which one planet gear isoperationally connected to the one sun gear and the one internal gearand the other planet gear to the other internal gear and the other sungear, these planet gears can be mounted on a common planet carrier.

One of the internal gears is assigned the input of the planetary gearset, the other one of the internal gears is designed fixed on thehousing, the one of the sun gears is connected to one of the driveshafts in a rotationally fixed manner and the other one of the sun gearsacts directly or indirectly, for example via an intermediate shaft, onthe other one of the drive shafts. Because of this, the input of theplanetary gear set is accessible from the outside, so that with regardto design the force flow generated by the motor of the drive unit can berouted to the input of the planetary gear set in a simple manner. Inthat, the outputs of the planetary gear set are assigned to the sungears the outputs are located close to the center of the planetary gearset, so that an operational connection of the outputs to the outputshafts can be realized in a technically simple manner. To this end, theintermediate shaft can for example be designed as internal shaft, withinwhich a section of one of the drive shafts is guided, more preferablymounted.

It can also be provided that one of the sun gears is assigned the inputof the planetary gear set, the other one of the sun gears is designedfixed to the housing, the one of the internal gears is connected to oneof the drive shafts in a rotationally fixed manner and the other one ofthe internal gears acts directly or indirectly on the other one of thedrive shafts. One of the sun gears is connected to an intermediate shaftdesigned as hollow shaft in a rotationally fixed manner, whichintermediate shaft acts on the input of the traction transmission andwithin which one of the drive shafts, on which an output of the tractiontransmission is acting, is arranged.

At least one electric motor is provided, through which the transmissionfor the output torques acting in opposite direction and/or thetransmission for the output torques acting in the same direction can bedriven. In that the drive unit for driving the one transmission and/orthe other transmission utilizes an electric motor, a mechanical wheeldrive with particularly low fuel consumption can be realized through thedrive unit. A substantial reduction of the fuel consumption isparticularly achieved when the drive unit is a rear drive unit in ahybrid vehicle, which comprises an energy storage unit or a battery,from which the energy for operating the electric motor is provided.

It can be provided, that the one transmission and the other transmissioncan be driven by a common electric motor. Two electric motors can alsobe provided, of which one electric motor serves for driving the onetransmission and the other electric motor for driving the othertransmission. Furthermore, it is conceivable that the at least oneelectric motor serves for driving the transmission for the outputtorques acting in opposite direction and for the transmission, whichgenerates output torques acting in the same direction, another drivetype such as for example a combustion engine, a fuel cell drive or thelike that is distinct from an electric drive can be provided as drive.It is substantial in this regard that the drive acting on thetransmission for output torques acting in the same direction is designedso that a propelling force moving the vehicle can be generated. Thisdrive can for example be dimensioned in such a manner that it serves asprimary drive for moving the motor vehicle in driving direction. Thisdrive as secondary drive can also be designed in order to permanently oractivatably support the one existing primary drive in order to generatean optimum propelling force for moving the motor vehicle in drivingdirection.

In principle, it is also conceivable that for generating the drivetorque, which acts on the transmission that generates the output torquesacting in the opposite direction, a drive concept other than an electricmotor is employed. To this end, any other desired drive system canobviously also be employed in order to influence the yaw angle of themotor vehicle by means of the transmission and thus bring about asteering effect. The drive system exerts a sufficiently large drivetorque on the transmission in order to generate the output torquesacting in opposite direction in a sufficient order of magnitude. It isappropriate that the electric motor, subject to the intermediateconnection of at least one spur gear transmission, more preferably of atwo-stage or three-stage spur gear transmission, acts on the onetransmission or the other transmission or traction transmission,preferentially subject to the intermediate connection of the shiftingdevice.

The drive unit comprises a trailing arm, on which the drive shaftssupport themselves directly or indirectly. Because of this, a sturdyaxle design, namely the twist-beam axle is utilized in order to installthe drive unit thereon, more preferably in order to support or mount thedrive shafts of the drive unit. Thus, the drive unit can be mounted on asturdy axle structure of the motor vehicle with little effort. Theentire drive unit including the trailing arm can be pre-assembled asassembly so that as a result advantages during the final assembly of themotor vehicle also materialize. Preferably, the trailing arm forms therear axle or at least a part of the rear axle, so that the drive unitserves a rear wheel drive, through which a propelling force for movingthe motor vehicle in forward driving direction or reverse drivingdirection can be utilized as primary drive or secondary drive supportingthe primary drive or through which a steering torque acting on the motorvehicle can be generated, which is achieved through the output torquesacting in opposite direction.

An all-wheel drive with a drive unit of the type described above is alsoprovided in accordance with an embodiment. An all-wheel drive as hybriddrive with a drive unit of the type described above is also provided inaccordance with an embodiment. In this case, the motor vehiclepreferably comprises a combustion engine, a drive such as a fuel celldrive or a drive other than an electric motor as primary drive. Thedrive unit of the type described above preferably serves as supportingsecondary drive that is driven by an electric motor and in support ofthe primary drive generates a propelling force or traction for movingthe motor vehicle in driving direction.

A motor vehicle is provided with all-wheel drive comprising a drive unitof the type described above.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction withthe following drawing figures, wherein like numerals denote likeelements, and:

FIG. 1 is a possible embodiment of a drive unit for an all-wheel driveof a motor vehicle in section representation with drawn-in force flow ina first operating mode;

FIG. 2 is the drive unit according to FIG. 1 with drawn-in force flow ina second operating mode; and

FIG. 3 is a further embodiment of a drive unit for an all-wheel drive ofa motor vehicle in top view.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and isnot intended to limit application and uses. Furthermore, there is nointention to be bound by any theory presented in the precedingbackground or summary or the following detailed description.

FIG. 1 and FIG. 2 show, in schematic representation, same possibleembodiment of a drive unit 1, which is preferably provided for use asrear drive unit of an all-wheel drive of a motor vehicle. The drive unit1 comprises two drive shafts 2, 3, of which one drive shaft 2 serves fordriving the one wheel (not shown) and the other drive shaft 3 fordriving the other wheel (not shown) of the motor vehicle. Preferably,the drive shafts 2, 3 are assigned to a common axle assembly for themotor vehicle.

The drive unit 1 furthermore comprises a motor, more preferably electricmotor 17, through which the drive shafts 2, 3 can be driven. The driveshafts 2, 3 can be driven by means of the electric motor 17 in two ways,as is evident by means of the force flows drawn into the FIG. 1 and FIG.2. In a first drive type (FIG. 2), the drive shafts 2, 3 are driven inthe manner that an output torque 200′ acting on the one drive shaft 2acts in the same direction with respect to an output torque 300′ actingon the other drive shaft 3. The two output torques 200′ and 300′substantially have the same amount, i.e., the same output torque istransmitted on the drive shafts 2, 3. To this end, the drive unit 1comprises a differential gear 7 known per se, through which a drivetorque 100 acting on the input 8 of the differential gear is dividedinto the two equally acting output torques 200′ and 300′. Through thedifferential gear 7, the circumferential velocities of the drive shafts2, 3 or of the wheels (not shown) of the motor vehicle driven by these,for example driving in curves, can freely establish themselves. In thisfirst drive type, the drive unit 1 serves for generating a propellingforce or traction in order to move the motor vehicle in drivingdirection.

In a second drive type (FIG. 1), the drive shafts 2 and 3 are driven inthe manner that an output torque 200 acting on the one drive shaft 2 isopposed in its operational direction with respect to the one outputtorque 300 acting on the other drive shaft 3. Because of this, the yawangle of the motor vehicle with its all-wheel drive is activelyinfluenced. Through the opposing output torques 200, 300, a steeringeffect is imparted on the motor vehicle in this second drive type,through which the dynamic driving behavior of the motor vehicle morepreferably when negotiating curves is improved.

In order to be able to provide the output torques 200, 300 opposing eachother on the drive shafts 2, 3 a transmission 4 is provided, which isdesigned as planetary gear set. Through the transmission 4, the drivetorque 100 acting on the input 5 of the transmission 4 is divided intothe two-output torques 200, 300 preferentially of the same amount, whichin their operational direction are opposed to each other.

In order to be able to switch the drive unit 1 from the one operatingmode into the other operating mode a shifting device 6 is provided,through which the force flow generated by the electric motor 17 can beoptionally directed to the input 8 of the differential gear 7 or to theinput 5 of the transmission 4. The shifting device 6 is preferably amechanical clutch, for example a claw clutch with or withoutsynchronizing gear.

Preferably, the shifting device 6 is designed to interrupt the forceflow to the drive shafts 2, 3 generated by the electric motor 17 in aneutral position. In this case, the shifting device 6 can thus beoperated in three modes. In a first operating mode, the force flow isdirected to the differential gear 7 by means of the shifting device 6.In the second operating mode, the force flow is directed to thetransmission 4 by means of the shifting device and in the third mode,the force flow is interrupted by means of the shifting device 6.

In order to realize the functioning method described above the driveunit 1 is preferably constructed as follows. The differential gear 7 andthe transmission 4 or planetary gear set are with their respectivetransmission axis each arranged coaxially with respect to the centeraxis 15 of the drive unit 1 and are located at a distance from eachother. The drive shaft 2 is connected in a rotationally fixed manner toa gear wheel 21, more preferably a bevel gear of the differential gear7. Likewise, the drive shaft 3 is connected in a rotationally fixedmanner to a gear wheel 22, particularly bevel gear of the differentialgear 7. The gear wheels 21, 22 of the differential gear 7 in this caseare located with their respective axis of rotation substantiallycoaxially with respect to the center axis 15 of the drive unit 1. Theinput 8 of the differential gear 7 is preferentially formed by thehousing of the differential gear 7, which interacts with at least onepreferentially two gear wheels 23, 24, preferentially bevel gears, ofthe differential gear 7. The gear wheels 23, 24 are located with theiraxis of rotation substantially transversely to the center axis 15 of thedrive unit 1, so that through a rotary movement of the housing of thedifferential gear 7 about the center axis 15 the gear wheels 23, 24 areco-rotated about the center axis 15 and in the process simultaneouslyrotate about their own gear wheel axis 25. In the process, the gearwheels 23, 24 roll on or mesh with the gear wheels 21, 22 that areconnected to the drive shafts 2, 3 in a rotationally fixed manner.

The input 8 of the differential gear 7 is connected to an intermediateshaft 16 in a rotationally fixed manner, which intermediate shaft isdesigned as hollow shaft. The intermediate shaft 16 and the drive shaft3 are located concentrically with respect to the center axis 15 of thedrive unit 1, wherein the drive shaft 3 passes through the hollow spaceof the intermediate shaft 16 designed as hollow shaft, more preferablysupports itself in a rotatable manner against the intermediate shaft 16.

The intermediate shaft 16 in turn is operationally connected to theshifting device 6, in particular, a part of the shifting device 6 can beconnected to the intermediate shaft 16 in a rotationally fixed manner.The shifting device 6 in turn is operationally connected to a gear wheelof a spur gear transmission 19 driven by the electric motor 17, inparticular, a component of the shifting device 6 can be connected to thegear wheel of the spur gear transmission 19 in a rotationally fixedmanner. Between the output shaft 26 of the electric motor 17 and thespur gear transmission 19 a further spur gear transmission 18 can beconnected.

The transmission 4 or planetary gear set has two sun gears 9, 10, whichare arranged located one after the other seen in the direction of thecenter axis 15 and are located coaxially with respect to the center axis15. The one sun gear 9 is connected to the intermediate shaft 16 and theother sun gear 10 to the drive shaft 3 in a rotationally fixed manner.The sun gears 9, 10 thus form the outputs of the transmission 4.

The transmission 4 or planetary gear set furthermore has two internalgears 11, 12, which are arranged one behind the other seen in thedirection of the center axis 15 and are located coaxially with respectto the center axis 15. Between the internal gear 11 and the sun gear 9,at least two planet gears 13 are provided whose teeth mesh with theinternal teeth of the internal gear 11 and the outer teeth of the sungear 9. Furthermore, between the internal gear 12 and the sun gear 10 atleast two planet gears 14 are provided, whose teeth mesh with theinternal teeth of the internal gear 12 and the outer teeth of the sungear 10. The planet gears 13, 14 are arranged located one behind theother seen in the direction of the center axis 15 and rotatably mountedon a common planet carrier 20 thereon. It is also conceivable that atleast one of the planet gears 13, 14 of the two planet gears 13, 14 isarranged on the common planet carrier 20 in a rotationally fixed manner

One of the two internal gears 11, 12, preferentially the internal gear11, forms the input 5 of the transmission 4 and can be operationallyconnected to the shifting device 6 via a shaft section 27, and is morepreferably connected to a component of the shifting device 6 in arotationally fixed manner. The other of the internal gears 11, 12,preferentially the internal gear 12 is connected to the housing (notshown) of the drive unit 1 in a rotationally fixed manner.

FIG. 1 shows the force flow for the operating state of the drive unit 1,in which the shifting device 6 is shifted in the operating mode with theoutput torques 200, 300 on the drive shafts 2, 3 acting in oppositedirections. As is evident from the continuous force flow line, the driveunit 1 in this operating state of the drive unit 1 the spur geartransmission 18 is driven by the electric motor or its output shaft 26,wherein the spur gear transmission 18 in turn drives the spur geartransmission 19.

From the spur gear, transmission 19 the drive torque 100 is transmittedto the shifting device 6, which in the present operating mode passes thedrive torque 100 on to the shaft section 27 and the internal gear 11molded thereon. From the internal gear 11 of the transmission 4 or theplanetary gear set the drive torque 100 is divided into the two outputtorques 200, 300 preferentially of the same amount by means of theplanet gears 13, 14 and the one output torque 200 via the one sun gear 9and the intermediate shaft 16 and the differential gear 7 passed on tothe drive shaft 2. The other output torque 300 is passed on to the otherdrive shaft 3 via the sun gear 10. Here, the output torque 300 on thedrive shaft 3 has the same operational direction as the drive torque 100as the input 5 of the transmission 4. The output torque 200 on the driveshaft 2 by contrast has an operational direction that is opposed to theoutput torque 300 or the drive torque 100.

FIG. 2 shows the force flow of the drive unit 1 in that operating state,in which the shifting device 6 is shifted into the operating mode forgenerating the output torques 200′, 300′ acting in the same direction.The force flow runs from the electric motor 7 as far as to the shiftingdevice 6 in the same manner as in the operating mode of the drive unit 1described above. From the shifting device 6, the force flow or thetorque is passed on to the intermediate shaft 16 and then forms thedrive torque 100 at the input 8 of the differential gear 7. Through thedifferential gear 7, a division of the drive torque 100 into thetwo-output torques 200′, 300′ of the same amount takes place that act onthe respective drive shaft 2 and 3. The output torques 200′ and 300′ aregenerated by the differential gear 7 acting in the same operationaldirection.

In the neutral position of the shifting device 6 that is not shown inthe FIG. 1 and FIG. 2 the intermediate shaft 16 and the shaft section 27are decoupled from the shifting device 6, so that the force flow to boththe differential gear 7 as well as the transmission 4 or the planetarygear set is interrupted. In the neutral position, the wheels (not shown)which are arranged on the drive shafts 2, 3 are not driven by the driveunit 1. The mode of operation of the drive unit 1 is described in thefollowing on the example of a motor vehicle with all-wheel drive, whichis moved through the primary drive in forward driving direction and isnegotiating a curve.

The drive unit 1 for example is deactivated first. The shifting device 6of the drive unit 1 to this end is in the neutral position. The forceflow both to the differential gear 7 as well as to the transmission 4 orthe planetary gear set is interrupted. The electric motor 17 can beadditionally switched off in the neutral position. In order to improvethe driving behavior of the motor vehicle when negotiating curves theshifting device 6 can be shifted from the neutral position in the mannerthat the drive unit 1 is in the second drive mode. The drive unit 1 isthen in a steering mode. The force flow generated by the electric motor17 is directed to the planetary gear set 4. The rotary movement of theelectric motor 17 acts on the internal gear 11, which forms the input ofthe planetary gear set 4. The transmission of the rotary movement fromthe internal gear 11 to the further components of the planetary gear set4 and from there to the drive shafts 2, 3 is then effected as alreadydescribed above. Through the direction of rotation of the electric motor17 it can be influenced in this drive mode of the drive unit 1 and withthe driving movement of the motor vehicle that happens to take place atthat moment, if a torque that is directed in opposite direction to thedirection of rotation of the wheels of the motor vehicle acts on thedrive shaft 2 or on the drive shaft 3.

Preferably, the step-up or step-down transmission ratios of thecomponents of the planetary gear set 4 are selected in such a mannerthat during straight-ahead driving of the motor vehicle and in thesecond drive mode of the drive unit 1 and electric motor 17 switchedoff, the wheels on the drive shafts 2 and 3 rotate with the samerotational speed and the internal gear 11 of the planetary gear set 4 issubstantially free of a rotary movement relative to the locationallyfixed internal gear 12. Insofar as the motor vehicle is negotiating acurve, a rotational speed differential between the two drive shafts 2and 3 occurs, as a result of which the internal gear 11 starts to rotateeither in the one direction or in the other direction relative to thelocationally fixed internal gear 12. For as long as the electric motor17 is switched off, the rotor (not shown) of the electric motor 17 isdragged along through the rotary movement of the internal gear 11. Byenergizing the electric motor 17, an acceleration of the internal gear11 in the dragged direction or a braking of the internal gear 11contrary to the dragged direction takes place depending on the directionof the generated torque of the electric motor 17 with the consequencethat on the drive shaft 2 or the drive shaft 3 a torque is generated,which acts against the direction of rotation of the wheels of the motorvehicle moving in driving direction and the steering effect is thusgenerated through the drive unit 1.

Switching over the drive unit 1 from the second drive mode, the steeringmode, to the first drive mode, the traction mode, brings about thatthrough the shifting device 6 the force flow generated by the electricmotor 17 is directed to the differential gear 7. Because of this, thesame-direction output torques 200′ and 300′ are generated on the driveshafts 2 and 3 even when negotiating a curve, which have a supportingeffect on the propelling force of the motor vehicle and thus support thelocomotion in driving direction of the motor vehicle. Through thedifferential gear 7, the same forces are transmitted to the drive shafts2, 3, whereas the angular velocity of the wheels connected to the driveshafts 2, 3 can freely establish itself. Upon a failure of the electricmotor 17 in the traction mode, the rotor (not shown) of the electricmotor 17 would be dragged along.

FIG. 3 shows, in schematic representation, a further possible embodimentof a drive unit 1′. Components of the drive unit 1′ according to FIG. 3,which is identical to or functionally the same as the components of thedrive unit 1 according to FIG. 1 and FIG. 2 are provided with samereference numbers, so that in this respect reference is made to thedescription regarding the drive unit 1 according to FIG. 1 and FIG. 2.

The drive unit 1′ according to FIG. 3 differs from the drive unit 1according to the FIG. 1 and FIG. 2 among other things in that a trailingarm 28 is provided, on which the drive shafts 2, 3 of the drive unit 1′support themselves. To this end, the trailing arm 28 preferentially haslateral leg sections 29, 30, in each of which a mounting 31, 32 isrotatably mounted, which serves for the mounting of a wheel (not shown)of the motor vehicle in a rotationally fixed manner. The mounting 31 isconnected to the drive shaft 2 and the mounting 32 to the drive shaft 3of the drive unit 1′ in a rotationally fixed manner, so that a rotarymovement generated by the drive unit 1′ is transmitted to the wheels(not shown) of the motor vehicle via the drive shafts 2, 3 and themountings 31, 32. The drive unit 1′ with the trailing arm 28 forms aunit that can be preassembled, preferentially a rear axle unit for themotor vehicle that can be preassembled.

The trailing arm 28 consists of two drawn longitudinal swing arms 33,34, which are preferentially interconnected near their axis of rotation35 by a cross-link 36, preferentially transverse profile. The cross link36 preferably has a substantially U or T-shaped cross section.Furthermore, the cross-link 36 is preferably dimensioned in such amanner that it twists during unilateral spring compression and extensionand acts as stabilizer.

Through the drive unit, operating a motor vehicle in an all-wheel driveis made possible with low additional fuel consumption compared with thepure front-wheel drive or rear-wheel drive, particularly when the driveunit is designed as rear-wheel drive unit and is employed in a hybridvehicle with energy storage unit. In addition to this, the drive unitmakes possible driving with clearly improved driving dynamics of themotor vehicle compared with the conventional mechanical all-wheeldrives, which is made possible because of the output torques acting inopposite directions between the left and the right wheel of the driveunit. Furthermore, the drive unit makes possible the use of an electricmotor that is relatively small in output, which is adequate for anoptimum drive of the drive unit. By operating the drive unit in thethree different operating modes through the shifting device aparticularly good traction at low speed of the vehicle materializesoverall.

While at least one exemplary embodiment has been presented in theforegoing summary and detailed description, it should be appreciatedthat a vast number of variations exist. It should also be appreciatedthat the exemplary embodiment or exemplary embodiments are onlyexamples, and are not intended to limit the scope, applicability, orconfiguration in any way. Rather, the foregoing summary and detaileddescription will provide those skilled in the art with a convenient roadmap for implementing an exemplary embodiment, it being understood thatvarious changes may be made in the function and arrangement of elementsdescribed in an exemplary embodiment without departing from the scope asset forth in the appended claims and their legal equivalents.

1. A drive unit of a motor vehicle, comprising: a first drive shaft configured to drive a first wheel of the motor vehicle; a second drive shaft configured to drive a second wheel of the motor vehicle; and a transmission operationally connected to the first drive shaft and the second drive shaft through which a drive torque acting on an input of the transmission is divisible into a first output torque and a second output torque through which an output torque of the transmission acting on the first drive shaft is reversible in an operational direction relative to the output torque of the transmission acting on the second drive shaft.
 2. The drive unit according to claim 1, further comprising a shifting device through which a force flow of the drive unit towards the input of the transmission is interruptible.
 3. The drive unit according to claim 1, further comprising a gear operationally connected to the first drive shaft and the second drive shaft through which the drive torque acting on the input of the gear is divisible into the first output torque and the second output torque acting in the same direction of which the first output torque is configured to act on the first drive shaft and the second output torque is configured to act on the second drive shaft.
 4. The drive unit according to claim 3, further comprising a shifting device through which a force flow of the drive unit towards the input of the gear is interruptible.
 5. The drive unit according to claim 3, further comprising a shifting device through which a force flow of the drive unit is optionally directed to the input of the gear.
 6. The drive unit according to claim 3, further comprising a shifting device through which a force flow of the drive unit is optionally directed to the input of the transmission.
 7. The drive unit according to claim 6, wherein the shifting device is configured to interrupt the force flow to the first drive shaft and the second drive shaft in a neutral position.
 8. The drive unit according to claim 1, wherein the transmission is a planetary gear set through the first output torque and the second output torque acting in opposite directions are generated on the first drive shaft and the second drive shaft.
 9. The drive unit according to claim 8, wherein the planetary gear set comprises at least two sun gears, at least two internal gears and at least one planet gear coupled with an inner circumference of the at least two internal gears and an outer circumference of the at least two sun gears.
 10. The drive unit according to claim 9, wherein one of the at least two internal gears is assigned the input of the planetary gear set, the other of the at least two internal gears is designed in a manner fixed to a housing, the one the at least two sun gears is connected to one of the first drive shaft or the second drive shaft in a rotationally fixed manner and the other one of the at least two sun gears is configured to act on the other one of the first drive shaft or the second drive shaft via an intermediate shaft.
 11. The drive unit according to claim 10, wherein one of the at least two sun gears is connected in the rotationally fixed manner to the intermediate shaft designed as hollow shaft, which acts on an input of another gear and one of the first drive shaft or the second drive shaft is arranged therein, on which an output of another gear is acting.
 12. The drive unit according to claim 1, further comprising at least one electric motor through which the transmission for the output torque acting in opposite direction is driven.
 13. The drive unit according to claim 3, further comprising an electric motor through which the gear for the output torque acting in the same direction is driven.
 14. The drive unit according to claim 13, wherein the electric motor is subject to an intermediate connection of at least one spur gear transmission and acts on the transmission.
 15. The drive unit according to claim 1, wherein the drive unit comprises a trailing arm on which the first drive shaft and the second drive shaft are self-supporting. 